1. Field of the Invention
The present invention relates to chain tension adjustment devices for use with chain driven rolls of yarn feed attachments for tufting machines.
2. Description of Related Art
Yarn feed attachments for tufting machines are made by a number of manufacturers. One such attachment is described in detail in U.S. Pat. No. 4,688,497. These attachments may be connected to a tufting machine by a horizontally disposed support frame as in the aforesaid patent. The support frame carries a plurality of transversely extending parallel drive shafts. The shafts are driven at different speeds, but are generally in synchronization with the reciprocation of the needles. Some shafts are driven at relatively high speeds while others are driven at relatively slow speeds. The frame usually includes a plurality of parallel longitudinally extending, vertically disposed support plates which support the drive shafts.
Disposed below the main frame are a plurality of pairs of yarn feed rolls, each pair being carried by a roll shaft journalled by a roll shaft support bracket secured to the frame. The roll shafts are also usually supported by the support plates of the frame. Each pair of the rolls are typically located on opposite sides of each support plate and are mounted at the ends of the roll shaft. On the ends of each shaft and within each roll is an electric clutch, the rolls being selectively engaged and disengaged from the common roll shaft by actuation of the individual clutch for that roll. Each roll shaft is driven from one of the drive shafts by one or more chains. Typically each roll has a roughened periphery so as to be capable of driving one or a plurality of yarns at the peripheral speed of the roll.
When chains are installed on the yarn feed attachment to connect the drive shafts to the rolls, they sometimes do not provide an optimum amount of tension required to properly operate the rolls. If the chains are too loose, they may come off or fail to properly drive the rolls which may result in broken yarn fed to the tufting machine causing the machine to be shut down, the yarn ends tied, and production resumed. Furthermore, if the chains are too tight, they may break causing the roll to stop and the yarn to break and another stoppage of the tufting machine.
Accordingly, a need exists to provide a chain tension adjustment device for a yarn feed attachment to provide a desired amount of tension to the chain to maintain the tufting machine in operation.